1. Field of the Invention
This invention relates generally to methods and apparatus for enhancing the performance of minimally invasive surgery. This invention relates particularly to surgical instruments that augment a surgeon's ability to perform minimally invasive surgical procedures. This invention relates more particularly to a novel articulated surgical instrument for minimally invasive surgery which provides a high degree of dexterity, low friction, low inertia and good force reflection.
2. Background of the Invention
Minimally invasive medical techniques are aimed at reducing the amount of extraneous tissue which must be damaged during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort, and deleterious side effects. Approximately 21,000,000 surgeries are now performed each year in the United States. It is estimated that 8,000,000 of these surgeries can potentially be performed in a minimally invasive manner. However, only about 1,000,000 surgeries currently use these techniques due to limitations in minimally invasive surgical instruments and techniques and the additional surgical training required to master them.
Advances in minimally invasive surgical technology could have a dramatic impact. The average length of a hospital stay for a standard surgery is 8 days, while the average length for the equivalent minimally invasive surgery is 4 days. Thus, the complete adoption of minimally invasive techniques could save 28,000,000 hospital days, and billions of dollars annually in hospital residency costs alone. Patient recovery times, patient discomfort, surgical side effects, and time away from work are also reduced with minimally invasive surgery.
The most common form of minimally invasive surgery is endoscopy. Probably the most common form of endoscopy is laparoscopy which is minimally-invasive inspection and surgery inside the abdominal cavity. In standard laparoscopic surgery, a patient's abdomen is insufflated with gas, and cannula sleeves are passed through small (approximately ½ inch) incisions to provide entry ports for laparoscopic surgical instruments. 
The laparoscopic surgical instruments generally include a laparoscope for viewing the surgical field, and working tools such as clamps, graspers, scissors, staplers, and needle holders. The working tools are similar to those used in conventional (open) surgery, except that the working end of each tool is separated from its handle by an approximately 12-inch long extension tube.
To perform surgical procedures, the surgeon passes instruments through the cannula and manipulates them inside the abdomen by sliding them in and out through the cannula, rotating them in the cannula, levering (i.e., pivoting) the instruments in the abdominal wall and actuating end effectors on the distal end of the instruments. The instruments pivot around centers of rotation approximately defined by the incisions in the muscles of the abdominal wall. The surgeon monitors the procedure by means of a television monitor which displays the abdominal worksite image provided by the laparoscopic camera.
Similar endoscopic techniques are employed in arthroscopy, retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy, sinoscopy, hysteroscopy and urethroscopy. The common feature of all of these minimally invasive surgical techniques is that they visualize a worksite within the human body and pass specially designed surgical instruments through natural orifices or small incisions to the worksite to manipulate human tissues and organs thus avoiding the collateral trauma caused to surrounding tissues which would result from creating open surgical access.
There are many disadvantages of current minimally invasive surgical technology. For example, existing MIS instruments deny the surgeon the flexibility of tool placement found in open surgery. Most laparoscopic tools have rigid shafts and are constrained to approach the worksite from the direction of the small incision. Additionally, the length and construction of many endoscopic instruments reduces the surgeon's ability to feel forces exerted by tissues and organs on the end effector of the tool. The lack of dexterity and sensitivity provided by endoscopic tools is a major impediment to the expansion of minimally invasive surgery.
Telesurgery systems for use in surgery are being developed to increase a surgeon's dexterity as well as to allow a surgeon to operate on a patient from a remote location. Telesurgery is a general term for surgical systems where the surgeon uses some form of servomechanism to manipulate the surgical instruments movements rather than directly holding and moving the tools. In a system for telesurgery, the surgeon is provided with an image of the patient's body at the remote location. While viewing the threedimensional image, the surgeon performs the surgical procedures on the patient by manipulating a master device which controls the motion of a servomechanism-actuated instrument. The surgeon's hands and the master device are positioned relative to the image of the operation site in the same orientation as the instrument is positioned relative to the act. During the operation, the instrument provides mechanical actuation and control of a variety of surgical instruments, such as tissue graspers, needle drivers, etc., that each perform various functions for the surgeon, i.e., holding or driving a needle, grasping a blood vessel or dissecting tissue.
Such telesurgery systems have been proposed for both open and endoscopic procedures. An overview of the state of the art with respect to telesurgery technology can be found in “Computer Integrated Surgery: Technology And Clinical Applications” (MIT Press, 1996). Moreover, prior systems for telesurgery are described in U.S. Pat. Nos. 5,417,210, 5,402,801, 5,397,323, 5,445,166, 5,279,309, 5,299,288.
However methods of performing telesurgery using telemanipulators still require the development of dexterous surgical instruments capable of transmitting position, force, and tactile sensations from the surgical instrument back to the surgeon's hands as he/she operates the telesurgery system such that the system the surgeon has the same feeling as if manipulating the surgical instruments directly by hand. A system's ability to provide force reflection is limited by factors such as friction within the mechanisms, gravity, the inertia of the surgical instrument and forces exerted on the instrument at the surgical incision.
What is needed, therefore, is a surgical instrument that increases the dexterity with which a surgeon can perform minimally invasive surgical procedures.
It would also be desirable to provide a dexterous surgical apparatus having a wrist with two degrees-of-freedom.
It would further be desirable to provide a wrist mechanism that has low friction in order to provide the surgeon with sensitive feedback of forces exerted on the surgical instrument.
It would still further be desirable to provide a surgical instrument having a wrist mechanism for minimally invasive surgery which is suitable for operation in a telemanipulator mechanism.